\begin{tikzpicture}
    \tkzDefPoints{0/0/M, 4/0/N}
    \tkzDefPoints{0.4/0.8/A, 3.5/1.5/B}
    \tkzDefPointBy[reflection=over M--N](A)  \tkzGetPoint{A'}
    \tkzInterLL(M,N)(A',B)  \tkzGetPoint{C}
    \tkzDefShiftPoint[C](1,0){C'}

    \tkzDrawSegments(M,N  A',B)
    \tkzDrawSegments[dashed](A,A'  A,C  A,C'  A',C'  B,C')
    \tkzLabelSegment[below, pos=0.9](M,N){$a$}
    \tkzLabelPoints[above](A,B)
    \tkzLabelPoints[below](A', C')
    \tkzLabelPoints[below,yshift=0.2em](C)
\end{tikzpicture}

